1. Field of the Invention
The present invention relates to a composite material panel structure having an anti-lightning function, which is formed from a composite material panel containing reinforcing fibers and used as a member such as a wind turbine nacelle cover, an aircraft, an automobile, a ship or a railway vehicle, and relates to a manufacturing method thereof.
2. Description of the Related Art
A resin-based composite material (to be referred to simply as a “composite material” hereafter) containing reinforcing fibers is greatly advantaged due to its low weight, and therefore recent years have witnessed rapid advancements in the application of this composite material to members such as wind turbine nacelle covers, aircraft, automobiles, ships, and railway vehicles.
An autoclave molding method in which a bag film is placed over a plurality of laminated prepreg material sheets, whereupon the resulting component is subjected to pressurization molding through vacuum suction and then subjected to further pressurization, heating, and curing in an autoclave is known as a method of manufacturing the composite material.
For example, Japanese Patent Application Publication No. H7-214680 discloses a method of manufacturing a fiber-reinforced resin composite material. In this manufacturing method, a thermoplastic resin film is laminated onto a prepreg, heat is applied thereto under pressure in order to cure the resin, whereupon the thermoplastic resin film is peeled away such that a roughened surface is formed on the surface. Further, a constitution in which another material, for example metal foil, a metal plate, or the like, is laminated onto an inner layer part of the prepreg is described.
In an autoclave molding method, baking and curing are performed while applying pressure using an autoclave, and therefore a strong composite material is obtained. However, since this method requires an autoclave, which is a large-scale facility, an increase in cost occurs, and therefore the method is not suited to mass production.
Hence, a vacuum assisted resin transfer molding (VaRTM) method not requiring large-scale facilities has attracted a great deal of attention as a method of manufacturing a composite material.
A typical conventional vacuum assisted resin transfer molding method will now be described.
First, as shown in FIG. 8A, a mold releasing film 103 is disposed on a fiber-reinforced base material 102 placed in a mold 101. Next, a mesh sheet (a flow medium) 104 is disposed on the mold releasing film 103, whereupon the resulting member is covered by a bag film 105. End portions of the bag film 105 are tightly sealed by sealing members 106. Next, as shown in FIG. 8B, an inner side of the bag film 105 is subjected to vacuum suction, whereupon a liquid resin is injected into an interior of the bag film 105 and cured. After the resin has been cured, the mesh sheet 104 and the bag film 105 are removed by peeling away the mold releasing film 103. FIG. 8C shows a composite material panel 108 constituted by the fiber-reinforced base material impregnated with the resin, which is obtained through the method described above.
When a plurality of these composite material panels are coupled for use as a cover of a large structure disposed outdoors or a component of an outer wall, lightning may cause damage which extends to internal devices, and therefore measures must be taken to provide resistance against lightning.
A wind turbine nacelle cover, for example, includes an anti-lightning structure such as that shown in FIG. 9. In the drawing, a nacelle cover 110 is formed from a plurality of coupled composite material panels 111. The composite material panels 111 are typically non-conductive, and therefore a shield wire 112 is disposed inside the nacelle cover 110. When a lightning bolt 120 strikes, a current is released to the ground via the shield wire 112.